Engineering Risk Assessments and the Law – A Guide for Lawyers

Background

When engineering disputes or health and safety prosecutions reach court, the concept of risk is central. Risk assessments are the primary mechanism by which engineers identify, evaluate and manage hazards in design, construction, and operation.

For lawyers, understanding what these assessments are, how they are prepared, and how the courts interpret “risk” and “foresight” is critical. Properly understood, they serve not merely as technical documents but as evidence of whether an organisation anticipated and controlled foreseeable risks.

Legal Principles

What is risk?

In R v Board of Trustees of the Science Museum [1993] 3 All ER 853, the Court of Appeal held that “risk” extends beyond actual harm to include the possibility of danger, i.e. an exposure to risk. The law is therefore preventive: liability can arise where a material danger exists, even if no accident has yet occurred.

In R v Chargot Ltd [2008] UKHL 73, the House of Lords clarified that the Health and Safety at Work etc Act 1974 (HSWA) is directed only at material risks – those which are more than trivial or fanciful. Once exposure to a material risk is proven, the burden shifts to the duty-holder to demonstrate that they took all reasonably practicable steps to prevent harm.

Foresight and the Tangerine Decision

In R v Tangerine Confectionery Ltd & Veolia ES (UK) Ltd[2011] EWCA Crim 2015, Hughes LJ provided important clarification on the meaning of foresight under English law.

He explained that the offence under the HSWA lies in exposing people to risk, not in causing injury. While an accident may be compelling evidence that a risk existed, causation is not an ingredient of the offence. The Act does not criminalise fanciful or remote dangers, but real, foreseeable risks that a reasonable employer should guard against.

Hughes LJ also clarified that foreseeability in this context does not require prediction of the precise accident that occurred. The legal test is whether the activity created a real and foreseeable risk to safety. Finally, he reminded juries that they must concentrate on whether a risk existed and whether reasonably practicable precautions were taken, rather than being drawn into debates about causation.

Together, Chargot and Tangerine confirm that the law is concerned with foresight, not hindsight – and with real, foreseeable risks, not theoretical ones.

Nature and Function of Engineering Risk Assessments

Engineering risk assessments are structured analyses designed to identify hazards, assess the likelihood and consequence of those hazards, and determine whether the existing or proposed controls are sufficient.

They are typically prepared by engineers or multidisciplinary safety teams and form a vital part of the evidence base in both civil and criminal proceedings. Their outputs—usually tables, matrices, or diagrams—document foresight and can demonstrate whether risks were known, evaluated, and addressed.

A well-structured risk assessment shows that an organisation systematically examined its operations for hazards, weighed the risks, and took proportionate steps to reduce them “so far as was reasonably practicable.”

Types of Engineering Risk Assessments

1. HazOp (Hazard and Operability Study)

A HazOp uses design drawings and process data to explore deviations from intended operation. A team applies “guide words” such as more pressure or less flow to identify how deviations could lead to unsafe outcomes.

2. HazAn (Hazard Analysis)

A HazAn is an early-stage qualitative review identifying hazards in the system or process environment.

3. FMEA (Failure Modes and Effects Analysis)

An FMEA examines each component for possible failure modes, their effects, and the detectability of those failures. The product is a Risk Priority Number (RPN).

4. LOPA (Layer of Protection Analysis)

LOPA analyses specific hazardous scenarios by quantifying initiating event frequency and the reliability of protective layers.

Other techniques, such as Fault Tree Analysis, Event Tree Analysis, and Bow-Tie Analysis, present the relationships between causes, failures, and consequences in diagrammatic form. All share a single purpose: to make foresight visible and auditable.

“Paper” Assessments vs. Practice

Courts consistently distinguish between a risk assessment that exists on paper and one that is implemented in practice. A well-formatted HazOp or FMEA can evidence forethought, but if it was copied from a template, never communicated to workers, or left unimplemented, it provides little protection.

In both Chargot and Tangerine, the real question was whether the employer foresaw and managed risk in practice. Effective risk assessments must translate into real operational measures—training, maintenance, supervision, and procedural compliance.

The courts are now alert to “tick-box” risk assessments that exist only to satisfy regulatory formality. Genuine compliance requires integration into day-to-day operations, reviewed and updated as work changes or incidents occur. The existence of a document alone is not enough; its use and enforcement are what matter.

Practical Implications for Lawyers

Risk assessments are often pivotal in establishing liability or defence under the HSWA. They provide a structured record of foresight, proportionality, and mitigation.

For the prosecution, the absence or inadequacy of a risk assessment can indicate a breach. For the defence, a well-constructed, regularly reviewed assessment demonstrates that the duty-holder took reasonably practicable precautions.

A Lawyer’s Practical Checklist

When reviewing a risk assessment in litigation or compliance work, a lawyer should begin by identifying who prepared the assessment and whether the author or team possessed the necessary competence and expertise. The timing of the document is equally important: it should have been produced contemporaneously with the work in question, not after the event to justify a position.

Next, attention should be given to the inputs. A valid assessment is grounded in the actual processes, equipment, and working conditions, not in generic templates or borrowed material. The methodology used also deserves scrutiny—was it a systematic, recognised process such as a HazOp or FMEA, or merely a superficial checklist exercise?

The outputs should be critically assessed. Do the tables, matrices, and conclusions demonstrate a real evaluation of likelihood and consequence, or do they consist of vague or formulaic statements? It is also essential to consider whether the recommendations identified were implemented in practice, or whether they remained theoretical.

A credible risk assessment will have been clearly communicated to the workforce and embedded in operational routines. Finally, a robust assessment is a living document—reviewed and revised after incidents, near misses, or any changes to the process.

By addressing these points, lawyers can distinguish between a robust, embedded assessment that provides genuine evidence of foressight and diligence, and a tokenistic paper exercise that maps the route to prosecution.

Conclusion

Risk in law means the possibility of danger, not the occurrence of harm. Foreseeability is broad: employers must anticipate material risks even if they cannot predict the precise accident. Engineering risk assessments are the operational translation of that duty, turning foresight into documented evidence.

However, courts look beyond the paperwork. The question is whether the assessment was understood, acted upon, and kept alive within the organisation. Lawyers who understand these principles—and can interpret the structure, method, and credibility of risk assessments—can more effectively analyse liability, challenge expert evidence, and advise clients on compliance and defence strategy.

Done well, a risk assessment is a shield. Done poorly, it is a roadmap for prosecution.

Austin is a C. Eng., F. I. Chem. E, and was for many years a Chartered Scientist. He has chaired many engineering risk assessment committees on high value capital projects and has advised the Engineering Council on the implementation of engineering fitness to practise proceedings. He was safety counsel to the families of the bereaved in the Public Inquiry into the Grenfell disaster and has appeared in many of the more prominent safety cases of recent years.